The field of art to which this invention pertains is the hydrocracking of a hydrocarbonaceous feedstock. Petroleum refiners often produce desirable products such as turbine fuel, diesel fuel and other products known as middle distillates as well as lower boiling hydrocarbonaceous liquids such as naphtha and gasoline by hydrocracking a hydrocarbon feedstock derived from crude oil, for example. Feedstocks most often subjected to hydrocracking are gas oils and heavy gas oils recovered from crude oil by distillation. A typical gas oil comprises a substantial portion of hydrocarbon components boiling above about 371° C. (700° F.), usually at least about 50 percent by weight boiling above 371° C. (700° F.). A typical vacuum gas oil normally has a boiling point range between about 315° C. (600° F.) and about 565° C. (1050° F.).
Hydrocracking is generally accomplished by contacting in a hydrocracking reaction vessel or zone the gas oil or other feedstock to be treated with a suitable hydrocracking catalyst under conditions of elevated temperature and pressure in the presence of hydrogen so as to yield a product containing a distribution of hydrocarbon products desired by the refiner. The operating conditions and the hydrocracking catalysts within a hydrocracking reactor influence the yield of the hydrocracked products.
One of the preferred hydrocarbonaceous products from a hydrocracking process is diesel or diesel boiling range hydrocarbons. Marketable products must meet minimum specifications and over the years, it has been recognized that due to environmental concerns and newly enacted rules and regulations, saleable products including diesel fuel must meet lower and lower limits on contaminants such as sulfur and nitrogen. Recently new regulations were proposed in the United States and Europe which basically require the complete removal of sulfur from liquid hydrocarbons which are used as transportation fuels such as gasoline and diesel.
Although a wide variety of process flow schemes, operating conditions and catalysts have been used in commercial hydrocracking activities, there is always a demand for new hydrocracking methods which provide lower costs and improved product characteristics. The present invention specifically relates to the use of a dividing wall distillation column to economically hydrocrack a hydrocarbonaceous feedstock while simultaneously producing ultra low sulfur diesel product.